1. Field of the Invention
The present invention relates to a method and system for data processing, and in particular to a method and system for handling mobile database overflow.
2. Description of the Related Art
A mobile communication system covers a plurality of service areas, each divided into a plurality of location areas, each consisting of one or more base transceiver stations (BSC).
FIG. 1 is a schematic diagram showing the architecture of a mobile communication system, consisting of the following functional elements.
A home location register (HLR) 100 regulates a database storing user data, comprising user parameters and location information, of mobile users, in which each user must be registered in HLR 100. A visitor location register (VLR) 120 stores and processes call connection information, such as cellular phone numbers of users, location area identifiers, and service parameters. A mobile switch center (MSC) 140 provides switching and call delivery functions to mobile stations (MS) in a regulated location area. A base station controller (BSC) 160 regulates one or more base transceiver stations (BS). A base station system (BSS), which is a wireless communication subsystem regulated by MSC 140 communicating with mobile stations, consists of a BSC and corresponding base transceiver stations.
A base transceiver station (BS) 165 is a small local wireless equipment, providing wireless interface for mobile stations. A location area (LA) 180, regulated by a mobile switch center, consists of base transceiver stations regulated by a BSC. Each location area may comprise one or more base transceiver stations and has a location area identifier (LAI) by which the mobile communication system identifies the location of a mobile user. To locate a mobile station, the described system can page the mobile station by broadcasting to the location area in which the mobile station is located.
A mobile database, namely a VLR, is located at each service area. A mobile station requests registration on the system when entering a service area and the VLR temporarily stores user data of the mobile station with successful registration, then deletes the user data of the mobile station, when the mobile station moves out of the service area. A VLR reaches its maximum capacity when a predetermined large number of mobile stations enter the same location area, preventing subsequent mobile stations entering the service area from successful registration.
A conventional method for solving the above problem is described as follows. The VLR deletes a registration record according to a policy to satisfy the requirement of a new registration request. The mobile user, whose user data is deleted by the VLR, is called an overflow user. The VLR enables the mobile station of the overflow user to be re-registered when the overflow user makes a call unsuccessfully, and the overflow user re-sends a call origination request. In addition, when someone makes a call to the overflow user, the VLR informs the base station controllers of all location areas regulated by the MSC, in which the overflow user is located, to search for the location of the overflow user by broadcasting.
The described method, however, makes a large scale broadcast to all base station controllers regulated by a MSC when delivering a call to an overflow user, hence utilizing more hardware and software resources and bandwidth of a wireless network. Therefore, a method and system to overcome the above described drawback is desirable.